Frey is the better keeper and has 6-7 years left in him, Id suggest when hes about 34 you bring in a young keeper to learn off him so that when he retires you have a quality player to take over from him.
Not only is Frey better but most of the squad like Frey (at least on my Fiorentina save) so I wouldn't risk upsetting the whole squad by not playing Frey.